1. Field of the Invention
The present invention relates to an air conditioning system for vehicles, and more particularly, to a two-layer flow air conditioning system capable of separately blowing internal and external air.
2. Background of the Related Art
Generally in heating a vehicle interior in winter, cold and dry external air is introduced in order to prevent any frost on a windshield, which results in a corresponding decrease in the temperature of the vehicle interior.
In order to solve the above problem, an air conditioning unit is developed to provide two-layer airflow. Such an air conditioning unit realizes two-layer flow of the internal/external air by providing the external air to an upper region of the vehicle interior and circulating the internal air through a lower region of the vehicle interior. The fresh and dry external air provided to the upper region reduces the frost occurring on the windshield to ensure a defrosting performance as well as refreshes a driver and/or a passenger. The warm internal air is provided to the lower region to enhance a heating ability in the vehicle interior.
A typical example of the air conditioning unit for providing the two-layer airflow as above is disclosed in Japanese Patent Publication H10-181336 with its technology as illustrated in FIG. 1.
The air conditioning unit 10 with the above two-layer air flowing system has a first blower fan 30 and a second blower fan 31 each installed in an external air inlet port 22 and an internal air inlet port 23 of an air conditioning case 20 separated by a partition 21.
Inside the air conditioning case 20, an evaporator E and a heater core H are respectively installed toward the inside of the air conditioning case 20 from internal/external air inlet ports 22 and 23 with a certain interval. In front of the heater core H, are installed first and second temperature adjusting doors 40 and 41 for selectively opening/closing an exit 24 in the upper front thereof. In the rear of the heater core H, is installed a baffle 50 substantially shaped as a section of the air conditioning case 20 for partitioning a region in the rear of the heater core H into the first and second flow passages P1 and P2.
In an upper inward side of the baffle 50, is installed a third temperature adjusting door 42 for opening/closing the first flow passage P1 between the heater core H and the baffle 50. In the inside wall of the air conditioning case 20 opposite to the upper end of the baffle, is installed the first floor door 43 for opening/closing an upper gate of the second flow passage P2. In the lower end of the baffle 50, is installed a second floor door 44 a free end of which comes into contact with a central portion of the heater core H or a baffle 44a for selectively opening/closing the first flow passage P1 or a floor opening 25.
In the second temperature adjusting door 41, its rear end is rotatably installed at a substantially middle height of the heater core H to open/close the heater core H from a central portion thereof to a lower portion thereof. The free end of the second temperature adjusting door 41 is arranged in a substantially middle portion of the evaporator E opposite to the partition wall 21 to separate the internal/external air.
In the first temperature door 40, its rear end is rotatably installed at the upper end of the heater core H and its free end is superposed on a baffle 24a of the above exit 24 or on the second temperature adjusting door 41 to selectively open/close the heater core H from the central portion to an upper portion or the above exit 24. Herein, the first and second temperature adjusting doors 40 and 41 cooperate with each other while being rotated by one actuator.
The undescribed reference numerals 26 and 27 each designate a defroster opening and a face opening, and 26a and 27a each designate a defroster opening door and a face opening door for respectively opening/closing the defroster opening and the face opening.
The operation of the air conditioning unit having the two-layer air flow system of such a conventional prior art will be described in detail hereinafter.
When a warm mix mode is selected, the first and second temperature adjusting doors 40 and 41 are disposed as thick lines while the first temperature adjusting door 40 shuts the exit 24 above the heater core H to open the heater core H from the central portion thereof to the upper portion thereof as well as the second temperature adjusting door 41 opens the heater core H from the central portion thereof to the lower portion thereof. The third temperature adjusting door 42 opens the first flow passage P1 in the rear of the heater core H while the first floor door 43 shuts the second flow passage P2. In the second floor door 44, its free end is directed toward the central portion of the heater core H to open the floor opening 25 while closing the lower portion of the first flow passage P1.
Herein, the second temperature adjusting door 41 and the second floor opening door 44 function as partition walls for dividing the inside of the air conditioning case 20 into an external air layer section in the upper region thereof and an internal air layer section in the lower region thereof.
The operation of the doors as above defines a two-layered airflow passage of upper and lower portions within the air conditioning case 20. Due to the compulsive blowing force of the blower fans 30 and 31, the external air passes through an upper portion of the evaporator E to flow along above the second temperature door 41 toward the heater core H. After passing through the heater core H, the external air is discharged from the defroster opening 26. The internal air passes through a lower portion of the evaporator E to flow along under the second temperature door 41 toward the heater core H. After passing through the heater core H, the internal air is discharged from the floor opening 25 as guided by the second floor door 44. However, the conventional air conditioning unit for providing the two-layer airflow has the following problems.
Since the second temperature adjusting door 41 guiding separation of the internal/external air while opening/closing the front of the heater core H performs the opening/closing operation while rotating about its rear end, the evaporator E is necessarily arranged at a position beyond a trace of the second temperature adjusting door 41, drawn due to rotation, so as to avoid any interference in rotation of the second temperature adjusting door 41. This inevitably leaves a gap G between the evaporator E and the free end of the second temperature adjusting door 41.
In the mix mode, the gap G causes the humid internal air, which passed through the lower portion of the partition wall 21, to leak into the upper section where the external air flows. This elevates the humidity of the external air to remarkably degrade the defrosting performance. Further, this internal air leakage remarkably lowers a heating eff0ect.
In the meantime, the conventional two-layer air conditioning system simply supplies the internal/external air introduced into the air conditioning case 20 through the selected opening or vent but fails to simultaneously supply the cold air and the warm air which have respectively passed through the evaporator E and the heater core H, thereby deteriorating the comfort within the vehicle.
Further, a general air control process is performed by 5 modes including Face, Bi-Level, Floor, Mix and Defrost Modes. Since the second floor door 44 is opened in a warm mode but the second floor door 44 is closed to prevent any heat-exchange with the heater core H in a cool mode, in the above five modes, the floor mode for opening the floor door 44 is divided into two modes for closing the floor opening 44 in cooling and opening the floor opening door 44 in heating and the mix mode is also divided into two modes for closing and opening the floor opening 44. This makes the entire air control process into seven modes, thereby sophisticating the entire mode control structure.